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Injector basics for LSJ

Old 08-03-2013, 10:14 AM
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Injector basics for LSJ

First, let me state that I am in no way trying to step on anyones toes here. I am simply trying to educate the LSJ world about injectors. I do not want to see people deal with the frustration I went through.

There seems to be a ton of misinformation floating around about injectors in general, let alone in the LSJ world. There is a couple injector offset tables floating around for our cars, and I have done the math and improved upon them. First thing I have found is for some reason the advertised offset tables for injectors in our cars simply do not work. They somewhat worked for the Siemens 60's and 80's, but not for an injector with a higher offset approaching 1ms. I recently ditched the Siemens 60's because they are simply the wrong injector for our car. It should honestly never be used. More about that later.

I bought some Bosch EV14 630cc injectors to use with my car. The advertised offset at 14v was just over 1ms, according to the Bosch spec sheet. I even received GM offset charts with them in the normal LS1-E40-E67 formats. My IFR and voltage multiplier tables were setup correctly. I interpolated the data into the LSJ charts and started the car. It was pig rich. I could not remove enough fuel from the MAF and VE tables to make it even close, as the minimum pulsewidth of our computers is .3ms.

I know you are thinking I did not set something up right, but I assure you it was. I even tuned my car when it was stock so I have a solid reference to fall back on. I scaled my tune by 50%, just like the LS guys do for big injectors and for hitting the 1.36 G/cyl wall. Nothing changed. On paper you should be able to swap injectors, and as long as your injector data is correct, you should not have to change any trims. In reality nothing is perfect and at max you should not see more than a 2-3% change in fueling if nothing else was changed but injectors.

What I have discovered and verified is the LSJ computer(P12) uses exactly 50% of the offset values. I cannot figure out why, and I hope someone can figure it out. I have verified these offset values are correct, and I will show you how. Try it. Bet you it works.

This is an exert from a Megasquirt document modified for our cars, since we do not have secondary VE table.....

Adjusting Injector Offset table
Determining the proper amplitude is done by adding an exact percentage to the base injector pulse width and ensuring that the result is the same percentage increase in AFR.

The injector offset value is added to the injector pulse width as the very last item before the total pulse width is sent to the hardware. The purpose of the offset is just to account for the opening time - closing time of the injector. The offset is not affected by temperature and other engine trims and that is why it is added after all the trims have been applied to the base fuel value.

This is how you set up your tune on an LSJ PCM:

Copy your current tune with all fuel trims off. Fail your MAF at 0Hz, and make sure the DTC is set to MIL on first error. You want to be full open loop for this test. Change all adder tables under open loop to 1, so no fuel is added. Save this tune as offset_test. Write this tune now.

Next, add 10% to the VE table of offset_test, and save it as offset_test+10%.

Set up a histogram to read the offset table. Its a preconfigued table in HP Tuners. Change the volts to read ignition voltage. Do not forget to add ignition voltage to your table so it will log it. This will tell you what voltage the PCM is using as a calculation, and you need to make sure it is the same between both test.

Fuel temperature and humidity can affect AFR a bit, but the fuel temperature should reach a steady state after 30-minutes of idling the engine and humidity usually stays constant unless the weather is changing quickly or it is early in the morning or late in the day. It is important to try to keep as many factors that affect AFR constant as possible so that you can focus on the injector offset.

With the AFR steady at 14.70 and voltage steady in your chart, shut the car off and load the offset_test+10% tune. Restart car, and let idle at least 5 minutes. The AFR should settle out to 13.23 (since (14.70 - 13.23) / 14.70 is 0.1). If the AFR ends up richer than this, then you had more of the pulse width coming from the base fuel map than you should have and the 10% trim actually gave you a larger trim. This means that you need to increase the injector offset at the voltage it is logging at (so your entire curve moves up) and decrease the base fuel by the same amount across the board (if you add 0.2ms to the offset, subtract 0.2ms from all the cells in the VE table). If the AFR settled out leaner than 13.23, then you had too much in the offset table and not enough in the base fuel table and you need subtract from the offset curve and add the same amount to the base fuel table.

Repeat the experiment again until the offset_test+10% produces exactly a 10% change in AFR. Once you have this, you know that your injector offset curve is right where it needs to be. You can do this for a single voltage, then add/subtract from the whole table and it should be very close.
I have performed this test for the stock injectors, 60lb Siemens, 80lb Siemens, and my Bosch 60lb injectors. With the offset tables exactly half, the change was 10% every time. I tried this at idle and at WOT, and results were the same.

Injector Selection.....and reasons why


The stock injectors are a split pattern dual cone spray injector. There is a huge reason for this, since our motors are a 4 valve design. There is an intake runner splitter right in front of the valves. The proper injector will spray right on the back of both valves for maximum fuel atomization and efficiency....just like the factory injectors does.

Stock injector:


Bosch injector I have:



Not an LSJ head, but same concept here:



basic spray patterns:



Siemens 60lb Deka specs including spray pattern:




And here is a good read too...
http://www.usrallyteam.com/index.php...ex&cPath=10_44

Problem here is most people slap in the Siemens 60 and 80 pound Deka injectors, which are a single pattern cone spray. This intake split is about an inch and a half away from the tip of the injector, so this single 26* cone is spraying right on the split before it is even broader than an inch. This is very very bad, as it causes the fuel to lose its atomization and leads to fuel pooling in the intake as well as very inconsistent transient fueling. This single factor right here is why the idle is so poor with these injectors. Many people tell me they got their car to idle great with these injectors, and I simply have to call bullshit. No way you can get this style injector to idle as smooth as stock. You can get them to idle OK with no surging, but not perfect.

The injector I chose is a Bosch EV14 injector, part number 0280158123. You have to use an adapter on the nozzle to make it work, but many injector shops have this adapter. They are slightly longer than 60mm(stock length) at 64.5mm, but I had no trouble since the stock fuel rail is at a 45 degree angle. The spray pattern is a split cone 25* just like the factory injector. They flow 60.5lb/hr @43.5psi, and [email protected] which is the stock LSJ fuel pressure. Another good point is the minimum linear pulse width is .711ms, compared to the 1.4 for the Siemens 60's. This is HUGE for our tiny motors, since idle is typically around 1.2, and deaccel is .7ish. My idle is as good if not better than factory right now, and transient fueling is very smooth with these.

More info about the injector I went with:
http://www.bosch-motorsport.de/en-US...2775993867.pdf

Pic of the Bosch injecter with the adapter:


I bought them from Fuel Injector Connection in Georgia for about $60 each. That makes them about $100 more than the Siemens, and it is money well spent. Ask for Jon there, and he will know exactly which injectors you need. He will put the tip adapters on them and they will be a direct drop in.

I started with the Siemens 60's, and I can tell you those are a terrible injector for a 4 valve motor. You want the injector to spray on the back of the valves, not at the intake split. Please do some research before you follow everyone else and purchase the Siemens.

If you are interested in the 100% correct and verified injector data for the LSJ send me a PM and I will provide it.

Last edited by lwrs10; 08-07-2013 at 10:08 PM.
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Old 08-03-2013, 01:21 PM
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Interesting. I'd want a split stream 60# injector. Still on gm 42# .
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Old 08-03-2013, 02:06 PM
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Finaly some proof..
Very good info here
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Old 08-03-2013, 03:09 PM
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fixed formatting and broken pics.
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Old 08-03-2013, 03:21 PM
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I'm running Siemens 60# injector right now. If I was to switch to the bosch EV14 mentioned above, would that mean I would have to get a new tune? or are the two injectors close enough in flow that i would be able to just swap them out?

Correct me if I'm wrong:

EV 14, # 0 280 158 123

429 g/min = 56.75lb/hr

Last edited by FrankSS/SC; 08-03-2013 at 03:38 PM. Reason: added info to question
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Old 08-03-2013, 04:02 PM
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Originally Posted by FrankSS/SC View Post
I'm running Siemens 60# injector right now. If I was to switch to the bosch EV14 mentioned above, would that mean I would have to get a new tune? or are the two injectors close enough in flow that i would be able to just swap them out?

Correct me if I'm wrong:

EV 14, # 0 280 158 123

429 g/min = 56.75lb/hr
You would have to get a retune. The offset tables are very different.

And you are correct converting the g/min. But, these injectors were flow tested and flowed 72.02lb/hr at 58psi, which is our stock fuel pressure.
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Old 08-03-2013, 04:54 PM
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Hmmm can't seem to find em so easy. Where they sold from? Google failed me
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Old 08-03-2013, 04:56 PM
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Did you get them for a decent price? I personally wouldn't bother at $100 a pop.
I feel like my EV1 60#s were idling way better than my stock 34#, but that's just me.
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Old 08-03-2013, 05:10 PM
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Good info!
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Old 08-03-2013, 09:01 PM
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Pretty sure they were right at $60 each and you can get em from Fuel Injector Connection in Georgia. Ask for Jon, and tell him you want the same injectors Randy in Florida bought. I even have all the copy and paste data for them now after a couple 100 hours of trial and error.

Last edited by lwrs10; 08-07-2013 at 09:49 PM.
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Old 08-07-2013, 10:04 PM
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updated post with more info
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Old 08-07-2013, 11:20 PM
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Very nice info, I have not been a fan of the 60lb injectors ever, and that was the primary reason I milked the stage kit injectors as long as I did.
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Old 08-08-2013, 01:41 PM
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how are the Mototron 80's that ZZP sells, compared to this data?

EDIT: nevermind --- I see now that seimens and mototron are the same thing. Well....****....I JUST bought 80's and harness two weeks ago, haven't even run em yet. Wish I had seen this before I bought.

Last edited by wayfarer; 08-08-2013 at 01:48 PM.
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Old 08-14-2013, 02:13 PM
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Would ev14's that were 66.5mm measured O ring to O ring fit into the LSJ fuel rail?
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Old 08-15-2013, 12:08 PM
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Same injectors are on eBay for 50 bucks a pop. Might do these down the road.
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Old 08-15-2013, 11:40 PM
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Originally Posted by BlackSSstg2 View Post
Would ev14's that were 66.5mm measured O ring to O ring fit into the LSJ fuel rail?
I would bet they would.

Originally Posted by HopnDude View Post
Same injectors are on eBay for 50 bucks a pop. Might do these down the road.

Do they have the tip adapters with them too?
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Old 08-15-2013, 11:50 PM
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Nice post and information, we need more people like you around here.
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Old 08-16-2013, 10:25 AM
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Originally Posted by lwrs10 View Post
I would bet they would.
I havent taken off the fuel rail, is there room to sneak a small washer between the rail bolts to take up any excess space?
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Old 08-16-2013, 10:31 AM
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Originally Posted by ItalianJoe1 View Post
Very nice info, I have not been a fan of the 60lb injectors ever, and that was the primary reason I milked the stage kit injectors as long as I did.
Same here buddy.

I've had zero issues with my 42's (48's @ our 58 psi rail pressure) over the past 6 years they've been installed.

By the way OP, nice thread
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Old 08-16-2013, 11:51 AM
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So I'm assuming that the same 60's are bad for other motors too (just picked up a set for the LAP, 2
2 with vvt).
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Old 08-16-2013, 05:06 PM
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I had been talking about the spray pattern issue years ago, but couldn't get any cooperation on solving the issue. I had been looking at setting up a 2 injector per cylinder conversion, but, never finished it. I still have some junk heads, so I might eventually get back to it.

Regardless, it is great to finally see someone get this information and a solution out there.

Thanks.
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Old 08-19-2013, 07:51 PM
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I want to give a big thanks to lwrs10 for providing this info! I bought the Bosch injectors and have noticed an awesome improvement is idle quality and low speed drivability that was driving me nuts! These injectors replaced Siemens 80lb injectors I had in the car and I'm so much happier with how the car drives
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Old 08-19-2013, 09:09 PM
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So the 5* single cone of the ID1k's must make your skin crawl

Not to be cantankerous, but the way you abhor the Siemens/Motron makes it sound like you'd say my car shouldn't even run with that tight of a cone. But oddly enough, Injector Dynamics have possibly the best atomization on the market. And with the correct data, they honestly behave very well at idle/ low load with a brfps compensating for their sheer size.

My point here, is that the spray angle isn't everything. Yes it can play a big role, but droplet size (atomization) is the biggest factor. Which comes from QUALITY injectors as opposed to the dirt cheap 60's and 80's that everyone loves.

(Edit: don't take me the wrong way, I think this is a great thread. There's just more to it than spray pattern)
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Old 08-19-2013, 10:03 PM
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Originally Posted by armcclure View Post
So the 5* single cone of the ID1k's must make your skin crawl

Not to be cantankerous, but the way you abhor the Siemens/Motron makes it sound like you'd say my car shouldn't even run with that tight of a cone. But oddly enough, Injector Dynamics have possibly the best atomization on the market. And with the correct data, they honestly behave very well at idle/ low load with a brfps compensating for their sheer size.

My point here, is that the spray angle isn't everything. Yes it can play a big role, but droplet size (atomization) is the biggest factor. Which comes from QUALITY injectors as opposed to the dirt cheap 60's and 80's that everyone loves.

(Edit: don't take me the wrong way, I think this is a great thread. There's just more to it than spray pattern)
I agree with you 100%. But there is no way you can argue that a split spray pattern injector is the best choice for a 4 valve motor such as the LSJ. While you can make the other injectors work well, imagine how much better it would behave with that same injector but split spray.
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Old 08-19-2013, 10:06 PM
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Awesome thread OP, nice to see someone dig this deep into an issue and share it with the cobalt community for free
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